Conventional portable telephones (cellular phones) have incorporated therein a sound generator (ringer) for notifying the user of incoming calls with sound and a vibration generator for notifying the user of incoming calls. One of the two generators is selectively usable according to the situation.
However, small devices such as portable telephones have little or no excessive space for accommodating both the sound generator and the vibration generator, and therefore encounter the problem of becoming greater in size if equipped with the two generators.
Accordingly, the present applicant has already proposed a compact notifying unit 2 having the functions of a sound generator and a vibration generator as shown in FIG. 2 (Japanese Patent Application No. 161399/1996).
The notifying unit 2 comprises, as housed in a common casing 21, a first vibrator 4 for producing chiefly sound, and a second vibrator 3 for producing chiefly vibration as illustrated. The casing 21 comprises a hollow cylindrical body 22, an annular front cover member 24 having a sound release aperture 25 and attached to an open front side of the body 22, and an annular rear cover member 23 attached to an open rear side of the body 22.
The first vibrator 4 comprises a circular first diaphragm 41 having its peripheral portion held between the casing body 22 and the front cover member 24, and a coil 42 fixed to the rear side of the first diaphragm 41. The first vibrator 4 has a resonance frequency in the audible range.
On the other hand, the second vibrator 3 comprises an annular second diaphragm 34 having its peripheral portion held between the casing body 22 and the rear cover member 23, an outer yoke 32 secured to the inner peripheral portion of the second diaphragm 34, a permanent magnet 31 fixed to the front side of the outer yoke 32, and an inner yoke 33 fixed to the front side of the magnet 31. The coil 42 of the first vibrator 4 is accommodated in an annular magnetic gap defined by opposed faces of the outer yoke 32 and the inner yoke 33. The second vibrator 3 has a low resonance frequency actually inaudible.
FIG. 5 shows the construction of the main circuit of a portable telephone having the notifying unit 2 described. The telephone is so adapted that when pressed, a manual button 14 enables the user to select notification with sound, notification with vibration or notification by simultaneous operation of both the sound and vibration means for alerting the user to incoming calls. According to the selection thus made, an alert setting circuit 55 sets the selected alerting method for the control circuit 54.
The main circuit comprises a sound signal generating circuit 61 for producing a sound drive signal a of audio-frequency (e.g., about 2 kHz) for notification with sound, a vibration signal generating circuit 62 for producing a vibration drive signal b of actually inaudible low frequency (e.g., about 100 Hz) for notification with vibration, and an adder 63 for adding together the two drive signals delivered from the respective circuits 61, 62 to prepare a combined drive signal a+b for notification with both sound and vibration. One of these three drive signals is selected by a switch 6 and fed to the notifying unit 2. The switch 6 is controlled by the control circuit 54 for a change-over.
As shown in FIGS. 6, (a) and (b), the sound drive signal a and the vibration drive signal b are each an intermittent signal involving repetition of on-state and off-state with a predetermined period (e.g., about 3 seconds) to give effective notification.
Radio waves transmitted by the base station are received by an antenna 1 shown in FIG. 5 at all times with a specified period. The signal received is frequency-converted and demodulated by a radio circuit 51 and then fed to a signal processing circuit 52, which extracts a digital sound signal and a control signal from the signal. The operation of the signal processing circuit 52 is controlled by the control circuit 54.
The control signal obtained from the signal processing circuit 52 is fed to an incoming call detecting circuit 53, whereby an incoming call is detected if any. On the other hand, the sound signal given by the circuit 52 is fed to an unillustrated sound signal processing circuit and then output from a speaker as sound.
When an incoming call is detected by the circuit 53, the control circuit 54 changes over the switch 6 in conformity with the alert setting by the manual button 14 to feed the sound drive signal a, vibration drive signal b or combined drive signal a+b to the notifying unit 2.
When the sound drive signal a is fed to the coil 42 of the notifying unit 2, the first vibrator 4 resonates, producing sound waves mainly, whereas when the vibration drive signal b is fed to the coil 42 of the notifying unit 2, the second vibrator 3 resonates to produce vibration mainly.
Alternatively when the combined drive signal a+b is selected, the first vibrator 4 and the second vibrator 3 operate, producing sound waves and vibration at the same time.
With small portable devices such as portable telephones, the capacity of the cell serving as the power source is limited. Especially in the case of the portable telephone, other circuits including the ratio circuit start to operate at the same time upon receiving an incoming call, so that the limitation involved is severe.
The portable telephone shown in FIG. 5 is adapted to prepare the combined drive signal a+b by adding the sound drive signal a and the vibration drive signal b together to cause the notifying unit 2 to produce both sound waves and vibration. At this time, the on period of the sound drive signal a and that of the vibration drive signal b are likely to overlap as shown in FIGS. 6, (a) and (b), so that the powder consumption increases markedly during the overlapping period as shown in FIGS. 6, (c).
Consequently, the power consumption exceeds the capacity of the cell, entailing the problem of interrupting the incoming call or conversation or causing trouble to other circuits.
An object of the present invention is to preclude marked increases in the power consumption of a notifying device which is adapted to give notification with both sound and vibration.